I just want to chime in here and point out there is a HUGE prolem with fake/knock off NGK and denso spark plugs being sold on both amazon and ebay...One of the most common issues with these fakes is they are not built with the correct amount of copper and resistence which causes them to explode just like the issue the OP thought he had in this thread. They also wear down very quickly. You can test the plugs with an ohm meter to see if they are fakes but bottom line is if you got one of those deals online which seemed too good to be true (all 6 plugs for around $20-30) they are likely fakes. They come in very convincing packaging. I almost fell for this recently myself.